Wind-induced Building Motion Research Articles

The effects of motion sickness and sopite syndrome on office workers in an 18-month field study of tall buildings

This study aims to quantify the effects of exposure to wind-induced building motion on office workers. 55 participants, across 8 buildings in Wellington, reported their comfort, health, cognitive performance, work performance and response behaviours, via an on-line survey over a period of 18 months. Each building was instrumented with a small accelerometer that measured building accelerations across the entire study period. The analysis used acceleration dose and mean exposure to building accelerations to predict occupant responses. Participants reported stronger perceptible motion with increases in acceleration dose; moderated by the natural frequency of the building. Increases in building accelerations were associated with higher levels of motion sickness and sopite syndrome (sleepiness), which caused large reductions in task-based effort, consequently leading to reductions in work performance; however, cognitive performance was only mildly affected. These findings provide additional evidence showing the adverse effects of exposure to building motion. The limitations of field research and implications for experimental motion simulator studies and future serviceability criteria are discussed.

The fundamental human response to wind-induced building motion

This paper identifies seven areas where an increase in our fundamental understanding of the human response to building motion will facilitate the design of next-generation serviceability criteria for wind-induced building motion. These advances in knowledge address: (1) understanding the effects of wind-induced building motion on occupants, (2) metrics for building performance assessment, (3) understanding of habituation to building motion, (4) potential and real benefits of education, (5) motion characteristics to predict adverse occupant effects, (6) differentiation between residential and office serviceability criteria, and (7) multidisciplinary research methods and measures used in occupant comfort research. Each is discussed with reference to engineering literature and incorporates a multidisciplinary perspective including psychological and physiological research. Finally, methodological issues in the occupant comfort literature are discussed and recommendations for future research are offered to facilitate the design of next-generation serviceability criteria for wind-induced building motion.

Occupant response to wind-excited buildings: a multidisciplinary perspective

The occupant response to wind-induced building motion is complex, governed by human physiology, and moderated by the psychological response to motion and discomfort within a sophisticated engineered environment. This paper aims to consolidate and critique the early research on the occupant response to building motion and to present recent multidisciplinary research that identifies a broader range of responses to, and consequences of, exposure to building motion. Recent field-based research shows that mild motion sickness, known as sopite syndrome, can cause significantly reduced work performance and occupant comfort. This is supported by laboratory-based physiological studies showing low-amplitude acceleration induces physiological changes in humans well below the threshold of motion perception (∼6·5 milli-g) which are consistent with the early onset of nausea. Current design criteria, based on perception thresholds, do not include the wider range of possible effects, particularly sopite syndrome and nausea. As a consequence, building occupants may suffer from a range of effects, including sopite syndrome and reduced work performance, that are not considered in current guidelines.

Sopite syndrome in wind-excited buildings: productivity and wellbeing impacts

ABSTRACTTall buildings vibrate in response to strong winds at frequencies below 1 Hz, which can cause motion sickness and sopite syndrome in humans. Sopite syndrome is characterized by sleepiness, low motivation and low mood that can reduce productivity in office workers. This paper uses recent multidisciplinary research to estimate the cost of building motion on organizations in tall buildings, and provides a framework for future research. The potential costs of wind-induced building motion to organizations are highly variable, depending on the local weather climate, but are likely to be significant in the long-term. It is argued that wind-induced building motion is a negative externality, a cost of inadequate design passed to building users. A three-factor approach towards reducing adverse impacts of wind-induced building motion is discussed: (1) further research investigating the characteristics of motion that provoke sopite syndrome, (2) create a new generation of serviceability criteria, and (3) regulations setting the maximum acceptable motion dose for office workers. This three-factor approach will likely produce comprehensive, yet usable, guidelines to develop strategies that reduce the adverse effects of motion on occupants in both new and existing buildings.

DETRIMENTAL EFFECTS OF WIND-INDUCED BUILDING MOTION ON OCCUPANT WORK AND TASK PERFORMANCE

We present recent multidisciplinary research conducted by psychologists, engineers and physiologists investigating the effects of wind-induced building motion on wellbeing, manual task performance and cognitive performance. In a sample of actual office workers, we show that sopite syndrome is the main consequence of exposure to wind-induced building motion. Sopite syndrome, a form of mild motion sickness characterized by drowsiness and low motivation, is the main cause of reductions in work performance. Experimental research shows that biomechanical properties of the human body are influenced by the frequency of motion, which amplifies body sway and interferes with task performance at 0.5 Hz, and to a greater extent with increases in acceleration. Exposure to motion induced sopite syndrome in some participants, who performed significantly worse than unaffected individuals. A new generation of serviceability criteria should aim to minimize sopite syndrome, motion sickness, motion induced body sway, and other psychological and physiological factors, rather than only address perception thresholds, which will likely allow engineers and designers to create a new generation of buildings that will ensure an improved level of comfort and performance for building occupants.

A longitudinal field study of the effects of wind-induced building motion on occupant wellbeing and work performance

The current study uses a longitudinal within-subjects design to investigate the effects of wind-induced tall building motion on occupant wellbeing and work performance. 47 office workers on high floors of wind-sensitive buildings and 53 control participants completed 1909 surveys across 8 months and over a range of wind conditions. The results show that the effects of building motion are emergent, as motion sickness develops after a duration of exposure to motion, which mostly manifest as symptoms of sopite syndrome, or low-dose motion sickness (tiredness, low motivation, distraction from work activities, and low mood), which occur at 2–3 times baseline rates. As motion sickness increases, work performance significantly decreases by 0.76–0.90 standard deviations below baseline. Affected individuals attempt to manage their own discomfort, and indicate a preference to work a different location during motion, take 30–40% longer breaks, and attempt to self-medicate using analgesics. Humans are adaptable, allowing most occupants to continue their work activities, but at reduced levels of performance and comfort. Design criteria for tall buildings should attempt to minimise the environmental stress of building motion on work performance and wellbeing rather than motion tolerance or formal complaint to building owners.

Occupant comfort in wind-excited tall buildings: Motion sickness, compensatory behaviours and complaint

1014 central business district workers in Wellington, New Zealand, were surveyed about their experiences of wind-induced building motion, susceptibility to motion sickness, reported compensatory behaviours, and complaints about building motion. Overall, 41.7% of the respondents reported that they had felt wind-induced building motion, and 41.6% of those respondents reported perceptible motion at least once a month. Difficulty in concentrating was the most frequently reported effect of building motion, reported by 41.9% of the respondents who had felt building motion. This suggests that early onset motion sickness develops in many building occupants. Despite a strong preference to avoid working in tall buildings, highly susceptible individuals were equally likely to work on high floors as low floors, increasing their potential exposure to building motion. These highly susceptible individuals were more likely to report symptoms of motion sickness due to building motion. Despite the reported adverse effects of motion sickness, building occupants in general almost never make formal complaints about building motion, contradicting the widely held assumption that complaint is an effective index of building performance. Some building occupants then actively compensate for the effects of building motion by taking more breaks and in some cases taking motion sickness tablets. Implications for occupant comfort, motion sickness, the rate of occupant complaint and compensatory behaviours are discussed.

Frequency Dependence of Human Response to Wind-Induced Building Motion

There has long been debate about the necessity of considering motion frequency in the assessment of occupant comfort during wind-induced tall building motion. This paper characterizes the biodynamic human body vibration response occurring during exposures to low-frequency, constant amplitude acceleration sinusoidal motion and demonstrates a physiological frequency dependence of this motion. The findings from a series of motion simulator experiments show that, as the frequency of oscillation increases from 0.15 to 1.00 Hz, acceleration measured at the head of a human test subject is increasingly magnified. This motion magnification demonstrates that biodynamic human body vibration is frequency dependent in this frequency range. Furthermore there may also be further implications for visual perception of motion through parallax shift. Clearly, these effects need to be accounted for in developing more refined occupant comfort acceptable criteria for tall building motion.

Viscoelastic damping for wind-excited motion of a five-story building frame

Abstract A 1/12 scale five-story full aeroelastic building model equipped with viscoelastic dampers is designed and tested in a boundary layer wind tunnel to investigate the effectiveness of viscoelastic dampers in suppressing wind-induced building motion. The degree of reduction in free-decaying curves and RMS accelerations is used as a measure of effectiveness of added viscoelastic dampers. Two different target damping levels, namely, 10% and 15% were pursued by different dimensions but the same kind of viscoelastic material. Experimental results show that significant improvement of structural performance under wind load can be realized with addition of viscoelastic dampers. Also the result of damper property tests show that when viscoelastic dampers are applied to wind-excited buildings or structures, in particular the number of loading cycles and strain range during a severe wind event must be taken into account.

Effect of tuned mass dampers on wind induced response of tall buildings

The effectiveness of a tuned mass damper in suppressing wind-induced building motion was examined through both a mathematical analysis and a wind tunnel test. The dependence of the optimized design parameters on the characteristics of random excitaion was indicated in the first part. A 1:1000 scaled aeroelastic model of CAARC standard tall building was chosen for the wind tunnel test to demonstrate the damper's effectiveness. It is also interesting to find that even with this small scale the test results show good agreement with the prviously published CAARC results from the other institutions.